Janus Films’ 50th-anniversary collection of 50 movies on DVD represents a significant chunk of cinematic history — “films like Michelangelo Antonioni’s ‘Avventura,’ François Truffaut’s ‘400 Blows,’ Fritz Lang’s ‘M,’ Akira Kurosawa’s ‘Seven Samurai’ and Luis Buñuel’s ‘Viridiana,’ along with dozens of others that constitute the backbone of the art house tradition.” So how did the little indie distributor compile such a catalogue? “At a time when rights to a foreign film in the United States could be had for less than $50,000, (the company) set about systematically acquiring the most prestigious films available, including some Hollywood classics.”